PAPER
Palladium-Catalyzed Synthesis of 5H-Imidazo[2,1-a]isoindoles
539
1:1) to give compound 3o (38.1 mg, 55%) as a pale yellow amor-
phous solid.
H-2), 7.26 (m, 3 H, m- and p-CH of Ph), 7.33 (dd, J = 7.4, 1.0 Hz, 1
H, H-8), 7.79 (d, J = 7.5 Hz, 1 H, H-9).
1H NMR (300 MHz, CDCl3): d = 3.78 (s, 3 H, OCH3), 3.92 (s, 3 H,
OCH3), 4.73 (s, 2 H, CH2-5), 6.42 (s, 1 H, H-8), 6.52 (s, 1 H, H-6),
7.04 (s, 1 H, H-3 ), 7.11 (s, 1 H, H-2).
13C NMR (75 MHz, CDCl3): d = 48.7 (CH2-5), 55.7 (OCH3), 55.8
(OCH3), 98.3 (CH-8), 100.7 (CH-6), 112.2 (C-9¢), 115.1 (CH-3),
133.1 (CH-2), 145.1 (C-5¢), 153.0 (CH-1¢), 154.5 (C-7), 161.4 (C-
9).
13C NMR (75 MHz, CDCl3): d = 63.9 (CH-5), 115.1 (CH-3), 120.0
(CH-9 and CH-6), 123.8 (CH-7 and CH of Ph), 127.1 (CH of Ph),
127.8 (CH of Ph), 128.7 (CH-8), 128.8 (C of Ph), 129.2 (2 CH of
Ph), 133.8 (CH-2), 137.7 (C-9¢), 147.2 (C-5¢), 153.1 (C-1¢).
HRMS (ESI+, MeOH): m/z [M + H]+ calcd for C16H13N2: 233.1079;
found: 233.1081.
HRMS (ESI+, MeOH): m/z [M + H]+ calcd for C12H13N2O2:
217.0977; found: 217.0987.
Acknowledgment
The authors thank M. T. Martin for helpful NMR expertise, Dr. D.
Guénard and Dr. F. Guéritte for their constant interest in this work,
and CNRS for financial support.
11H-Benzo[e]imidazo[2,1-a]isoindole (3p)
Prepared as described on general procedure A from 2p (0.30 mmol).
Purification on preparative TLC (Et2O–EtOAc, 1:1) afforded pure
3p (10.8 mg, 17%) as a yellow oil. The numbering of 3p skeleton
for NMR assignments is shown in Figure 2.
References
1H NMR (300 MHz, CDCl3): d = 5.19 (s, 2 H, CH2-5), 7.25 (s, 1 H,
H-2), 7.29 (s, 1 H, H-3), 7.53 (m, 2 H, H-7 and H-8), 7.73–7.79 (m,
1 H, H-9), 7.89–7.98 (m, 3 H, H-6,10,11).
13C NMR (75 MHz, CDCl3): d = 48.5 (CH-5), 116.3 (CH-3), 118.1
(CH-9), 122.4 (CH-6), 126.1 (CH-8), 127.2 (CH-7), 127.9 (C-11¢),
128.9 (C-6¢), 129.2 (CH-9), 129.4 (CH-10), 132.8 (C-9¢), 133.2
(CH-2), 138.7 (C-5¢), 155.9 (C-1¢).
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HRMS (ESI+, MeOH): m/z [M + H]+ calcd for C14H11N2: 207.0922;
found: 207.0934.
(e) Kawasaki, I.; Taguchi, N.; Youko, Y.; Yamashita, M.;
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4
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9'
9
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Figure 2 Numbering of the tetracyclic skeleton in 3p
(5,5-Dimethyl)-5H-imidazo[2,1-a]isoindole (3q)
Prepared as described in general procedure A from 2q (103 mg,
0.33 mmol). The residue was purified by preparative TLC (Et2O–
EtOAc, 1:1) to afford compound 3q (24.3 mg, 40%) as an amor-
phous solid.
1H NMR (300 MHz, CDCl3): d = 1.57 (s, 6 H, 5-CH3), 7.04 (d, J =
1.2 Hz, 1 H, H-3), 7.18 (d, J = 1.2 Hz, 1 H, H-2), 7.29 (d, J = 1.3
Hz, 1 H, H-6), 7.32 (m, 2 H, H-7,8), 7.77 (d, J = 7.4 Hz, 1 H, H-9).
13C NMR (75 MHz, CDCl3): d = 28.7 (2 CH3), 63.8 (C-5), 113.6
(CH-3), 121.0 (CH-9), 122.3 (CH-6), 128.6 (CH-8), 129.2 (C-5¢),
129.3 (CH-7), 134.2 (CH-2), 151.7 (C-1¢), 153.2 (C-9¢).
HRMS (ESI+, MeOH): m/z [M + H]+ calcd for C12H13N2: 185.1079;
found: 185.1090.
5-Phenyl-5H-imidazo[2,1-a]isoindole (3r)
Prepared as described in general procedure A from 2r (75.6 mg,
0.21 mmol). The residue was purified by preparative TLC (Et2O–
EtOAc, 1:1) to afford compound 3r (28.9 mg, 59%) as a pale yellow
amorphous solid.
Prepared as described on general procedure B from 2r (108 mg,
0.30 mmol). The residue was purified by preparative TLC (Et2O–
EtOAc, 1:1) to afford compound 3r (49.5 mg, 71%) as a pale yellow
amorphous solid.
1H NMR (300 MHz, CDCl3): d = 5.84 (s, 1 H, H-5 ), 6.93 (s, 1 H,
H-3), 7.04 (m, 2 H, o-CH of Ph), 7.16 (m, 2 H, H-6,7 ), 7.18 (s, 1 H,
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Synthesis 2007, No. 4, 529–540 © Thieme Stuttgart · New York